I'm pretty much broke all the time, so that means that the PortaPro's are the best headphones I've been able to own. Don't get me wrong, I love them, but they're definitely not top-of-the-line. Even though I consider them the best headphones I've owned, I rarely used them because they're open headphones, meaning they have zero isolation. I decided that that could be fixed, and here's how I did it.

I bought some low-profile, folding Peltor hearing protection, drilled some holes, sanded and painted, soldered some stuff, and came up with this:

I drilled a hole on the top for ventilation, since open headphones require airflow. I also put metal mesh over it for looks, and glued the PortaPro badge on.

I drilled 3 holes in the bottom for more air flow, and I decided to make the cord come out of the front face rather than the bottom, purely for cosmetics originally, but it turned out to be nice since it keeps the cords off of my neck.

The drivers sit under the foam that came with the hearing protection

I had to splice the wires to get the cords through the holes I drilled. I fed them through, soldiered them up, and then put heat shrink tubing around them.

There is an effect on the sound quality. Putting the PortaPros in a closed environment made them sound less clear, and just generally more like closed headphones do. It's a worthy sacrifice, and if I did it again I think I could make them sound better by drilling the holes in more ideal locations.